Circadian rhythms are outputs of the internal clock that regulates the daily functions of almost all living organisms. Circadian rhythms are typically 24 hours because they are synchronized by external cues such as the natural light/dark cycles of the environment. When external cues are removed, the circadian rhythm “free-runs,” thus revealing the organism’s endogenous circadian period. Recent studies have found that the trashline orbweaving spiders Cyclosa turbinata and Allocyclosa bifurca have abnormally short circadian rhythms of approximately 19 and 18 hours, respectively. Trashline orbweavers construct a line of debris made of prey carcasses in the center of their web and then remain undetectable by being cryptic within their trashline. Despite similar circadian rhythms and web-building behaviors, recent genetic findings indicate that these species actually are not closely related. In fact, both genetic and morphological data now suggest A. bifurca is more closely related to Cyrtophora citricola, the Tropical Tent-web spider. This would suggest that trashline behavior and exceptionally short circadian clocks evolved independently in C. turbinataand A. bifurca. This study analyzed the circadian rhythm of C. citricola and compared it to the circadian rhythm of A. bifurca. If C. citricola has an abnormally short clock like A. bifurca, this would indicate that the evolution of the short clock preceded the divergence of these species’ lineages. However, if C. citricola has a more typical clock, this would suggest that the unusually short clock evolved in the A. bifurca lineage and may be more ecologically linked to the trashline behavior. Thirty-two female C. citricola were collected in Southern Florida and had their locomotor activity measured over four days of 12:12 light/dark cycles followed by complete darkness to determine their circadian free-running periods (FRP). Cyrtophora citricola was found to have a more typical FRP of 24.0 + 0.43 hours. Despite being closely related, C. citricola and A. bifurca differ significantly in their circadian rhythms, suggesting that short circadian rhythms may be ecologically linked with trashline behavior.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:asrf-2109 |
| Date | 25 April 2023 |
| Creators | Upham, Jessica, Jones, Thomas, Moore, Darrell |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Source | Appalachian Student Research Forum |
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